An organic light emitting diode (OLED) display device is one of hot topics in the research field of flat panel display. Compared with a liquid crystal display, the OLED display device has advantages of low power consumption, low production cost, self-luminescent, broad view angle and fast response speed and so on. At present, in the flat panel display field such as mobile phone, PDA and digital camera and the like, the OLED display device has taken the place of the traditional LCD display screen.
The configuration of the OLED display device mainly comprises: an underlay substrate. Light emitting of the organic light emitting pixel unit OLED display device manufactured on the underlay substrate is realized as follows: a voltage is applied between an anode and a cathode by a pixel circuit, holes in the anode and electrons in the cathode are composite at an organic light emitting layer to produce excitons; the excitons are migrated under the effect of electric fields to deliver energy to luminescent molecules in the light emitting layer and excite electrons in the luminescent molecules to leap from a stationary state to a an excitation state, and the excitation state energy produces photons through radiated leaping.
Unlike that LCD controls the luminance by using a stable voltage, OLED pertains to current-driving, and a stable current is required to control light emitting. Due to manufacturing processes, device aging and so on, non-uniformity exists in a threshold voltage Vth of a driving transistor in the most traditional 2T1C pixel circuit, thereby resulting in that a change occurs in the current flowing through OLED of each pixel point to cause the displaying luminance to be non-uniform, which influences display effect of the entire image, such that phenomenon of non-uniformity occurs in the OLED devices of difference areas.
At present, in order to compensate for non-uniformity of the threshold voltage of the driving transistor in the pixel circuit, the number of thin film transistors and capacitors is increased in the pixel circuit, and threshold voltage drift of the driving transistor in the pixel circuit is offset by mutually matching between the thin film transistors and the capacitors. However, the increase of the number of the thin film transistors and the capacitors in the pixel circuit would cause the reduction of the pixel size to be limited greatly, thereby influencing the display effect of pixels.
Therefore, in the case that there are a large number of thin film transistors in the pixel circuit in the existing organic light emitting display device, how to raise the display effect of the pixels becomes a focus of respective manufacturers.